Photographic process



United States Patent PHOTOGRAPHIC PROCESS Edwin H. Land, Cambridge, Mass., assignor to'Polaroid Corporation, Cambridge, Mass., a corporation of Delaware Filed July 5, 1956, Ser. No. 595,988

7 Claims. (Cl. 96-29) This invention relates to photographic processes and, more particularly, to methods of producing sequential photographic images.

An object of the present invention is to provide a method of producing sequential photographic images, said method including the production of a photographic image on the rear surface of a previously exposed and processed photosensitive element. v

Another object of the invention is to provide a method of producing a sequence of photographic prints, said method employing a plurality of photosensitive elements, each including a photosensitive material and at least one of which is capable of forming a support for a photographic print.

Further objects of the invention are: to provide a method of producing a sequence of photographic prints, said method employing at least a first photographic element including a photosensitive layer and a layer capable of supporting a photographic transfer print, and a second element including a photosensitive layer, and including the steps of photoexposing and processing the photosensitive layer of said first element, photoexposing the photosensitive layer of said second element and superposing said exposed photosensitive layer of said second element with the support layer of said first element and forming a print on said support layer by a fluid composition distributed between said elements; and to provide, in a method of the type described, the additional steps of separating said first and second elements when formation of 'said print is completed, and removing the processed photosensitive layer of said first element from said support carrying said print.

Other objects of the invention will in part be obvious and will in part appear hereinafter.

The invention accordingly comprises the process involving the several steps and the relation and order of one or more of such steps with respect to each of the others which are exemplified in the following detailed disclosure, and the scope of the application of which will be indicated in the claims.

For a fuller understanding of the nature and objects of the invention, reference should be had to the following detailed description taken in connection with the accompanying drawing wherein:

Figure 1- is a diagrammatic, enlarged, sectional view of a composite photographic element of the type employed in the method of the invention;

Fig. 2 is a view, similar to Fig. 1, illustrating a step in the method of the invention; and

Fig. 3 is a diagrammatic, partial, sectional view of photographic apparatus in the form of a camera and illustrating the method of the invention.

Thepresent invention concerns a novel method of producing a sequence of photographic prints by silver transfer reversal, and involves the use of a plurality of photographic elements, each including a photosensitive stratum and at least one of which includes a print-receiving stratum capable of supporting a transfer print and 2,972,532 Patented Feb. 21, 1961 fi ice located on the side of the element opposite the photosensitive stratum. Each successive print is produced by exposing the photosensitive stratum of one of the elements and superposing said stratum with the print-receiving stratum of the previous element, the photosensitive stratum thereof having already been exposed and processed. A fluid composition, capable of processing the photosensitive stratum to produce a print on the printreceiving stratum, is distributed between the two elements. When the processing is complete, the two elements are separated from one another and the element containing the print may be subjected to a further treatment to remove the exposed and processed photosensitive stratum therefrom. The other element, containing the most recently exposed and processed photosensitive stratum and which may also include a print-receiving stratum, may be employed thereafter with the photosensitive stratum of the next successive photographic element to produce a print.

As indicated, the present invention involves the production of photographic prints by a silver transfer process in which a silver halide emulsion is differentially exposed and processed by a fluid composition distributed preferably in a layer on said emulsion between the latter and a second surface. This second surface preferably comprises a material capable of receiving and supporting a silver image deposited by reduction of a silver salt or complex formed in the fluid composition from unexposed silver halide. Examples of processes of this type, together with photographic materials useful therein, are described in detail in Letters Patent No. 2,543,181, issued February 27, 1951.

A preferred form of composite photographic element useful in the method of the present invention is illustrated at 10 in Fig. 1 of the drawing. Photographic element 10 is described for purposes or" illustration as comprising a photosensitive element and a print element, the photosensitive element comprising a photosensitive layer 12 and a stripping layer 14, and the print element comprising a support 16 and a print-receiving layer 18. Photosensitive layer 12 preferably comprises a gelatino silver halide emulsion, while support 16 comprises a suitable material such as paper, sheet plastic or glass, and is opaque to light actinic to photosensitive layer 12. Stripping layer 14, whose nature and function will be described more fully hereinafter, is provided on the forward surface of support 16 between the latter and photo sensitive layer 12, and by a suitable selection and treatment of layer 16, layer 18 may be an integral extension thereof, for example, layer 16 may be a cellulose ester and layer 18 may comprise the regenerated surface thereof. Print-receiving layer 18 is located on the rear surface of support 16 and may be of the type described in the aforementioned patent, and includes minute silver precipitating particles or nuclei for accelerating and increasing the precipitation of metallic silver from a fluid layer containing a silver salt or complex. However, in a preferred form of photographic element It), layer 18 is particularly adapted to serve as a support for a layer of fluid composition which forms a film on layer 18 and in which a visible silver transfer image is produced. Layer 18 for this purpose may contain agents for stabilizing the transfer image, examples of materials of this type useful in layer 18 being described in Letters Patent No. 2,662,822, issued December 15, 1953.

The fluid composition employed for processing a photo graphic element of the type described preferably includes an aqueous alkaline solution of a silver halide developer, a silver halide solvent and a film-forming agent. This fluid composition is indicated at 19 and, when distributed in a thin layer between an exposed photosensitive layer and the print-receiving layer of a photographic element .when processing of the print has been completed.

10, reduces the exposed silver halide to silver and reacts with unexposed silver halide to form a soluble silver cornplex which in turn is reduced to silver in a silver-receptive environment. This silver-receptive environment includes minute silver precipitating particles provided in a printreceiving layer 18 or in the fluid layer itself, as disclosed in the aforementioned Patent No. 2,662,822.

The fluid composition 19 for processing each photographic element is preferably supplied in a rupturable container 20 adapted to unidirectional discharge of its fluid contents when subjected to compressive pressure and associated with photosensitive layer 12 adjacent one edge of the area of said layer adapted to be exposed. The fluid composition is distributed in a thin layer between a pair of photographic elements, as shown in Fig. 2, by advancing the elements, commencing in the region of the container, between a pair of pressure-applying members. Since each processed photographic element is adapted to form the support for the next successive photographic print and as such must be moved between a pair of pressure-applying members, it is preferable that the fluid composition distributed between photosensitive layer 12 and print-receiving layer 18 adhere to the print-receiving layer when a photographic element containing a print is separated from the next successive element containing the photosensitive layer from which the print was produced y virtue of this arrangement, the processed photosensitive layer of a photographic element is free of the layer of fluid composition 19 so that the element may be advanced in superposition with another photographic ele ment petween a pair of pressure-applying members without contaminating the pressure-applying members with any residue of the fluid composition previously employed to process the photosensitive layer.

As mentioned above, the silver image comprising the print is preferably produced in the layer of fluid-composition 19 which remains on the print-receiving layer 18 when the two photographic elements 10 are stripped apart.

solution. Processes of this type, together with examples of solutions employed therein, are described in copending application Serial No. 555,433, filed December 27, 1955. The solution employed to protectively treat the image performs the added function of removing the photosensitive layer from the print, and, for this purpose, stripping layer 14 preferably comprises a material which is substantially unaffected by fluid composition 19, but is soluble in or at least softened by the solution used to protectively treat the image. Materials useful in intermediate stripping layers between an emulsion and its support are well known in the art and may include, for example, materials which are relatively unaffected by alkaline solutions such as would be present'in fluid composition 19, but would be soluble in or softened by an acid solution employed to protectively treat the print.

The herein described treatment of the photographic element for protecting the image-containing fluid layer of the print and for removing the processed photosensitive layer therefrom could be advantageously carried out with the aid of a device of the type described in copending application Serial No. 555,461, filed December 27, 1955, wherein a print may be immersed in a solution of the type desired and is subjected to a squeegeeing action as it is removed therefrom so that the print may be tactually dry.

Apparatus of the type adapted to the production of a sequence of photographic prints by the method of the invention is shown in Fig. 3 in the form of a camera 30. This camera comprises a housing mounting a conventional lens and shutter assembly 32, and having at its rear a chamber 34 in which are positioned a plurality of photographic elements li), substantially as described and arranged in stacked relation. Chamber 34 may be provided as a component of the camera or the photographic elements may be supplied in suitable means forming the chamber and adapted to be attached to the camera housing or introduced therein. Portions of the walls of the camera housing, indicated at 36, are adapted to engage the forwardmost element 10 so as to position the latter for exposure with its photosensitive layer at the focal surface of the lens of assembly 32. A spring 38 and pressure plate 40 are provided at the rear of chamber 34 for urging the photographic elements forward against wall portions 36.

As a means for superposing a pair of photographic elements and spreading fluid composition 19 in a thin layer therebetween, the camera preferably includes a pair of pressure-applying rolls 42 and 44 located adjacent one end (the lower end viewing Fig. 3) of chamber 34. Rolls 42 and 44 are mounted in juxtaposition with their axes substantially parallel and in a plane inclined obliquely to the focal surface of the lens of the camera and are so positionedwith respect to chamber 34 that the foremost photographic element, when moved downward in the focal surface of the lens of assembly 32, is advanced into the bite of the rolls. Suitable means, including for example a manually operable crank (not shown), are provided for rotating the rolls so as to advance photographic elements rearwardly between the rolls from the camera through a slot 46 provided in the housing of the camera at the lower rear portion thereof. The camera is provided with means such as a pair of friction wheels 48 located in the lower portion of the camera forwardly of the focal surface in position to engage the forwardmost photographic element at its lateral margins. Wheels 48 are provided with a friction-generating surface so that, when the wheels are rotated and a photographic element is held incontact therewith due to the force exerted by spring 38, the element is moved into the bite of rolls 42 and 44. Manually operable means in the form of a crank may be provided for rotating wheels 48 in a counterclockwise direction viewing Fig. 3.

A shallow chamber 50 is provided in the lower portion of the camera housing for positioning a print element adapted to be superposed with a photographic element following exposure of the latter. Chamber 50 is provided between a lower wall 52 of the housing and a hinged door 54 which provides access to chamber 50. A print element, indicated in the drawing at 56, is positioned Within chamber 50 with one end located in the bite of rolls 42 and 44 so that the element is drawn therebetween when the rolls are rotated. So that door 54 may be opened without danger of light entering the camera and exposing .a photosensitive element located therein, suitable lightshielding means, for example in the form of pads of a pile or. like fabric indicated at 58, may be provided at the end of chamber 50 closest rolls 42 and 44.

photographic element is positioned with the photosensitive layer thereof facing forward and includes a container 20 mounted at the lower end of its forward surface. The photosensitive layer of the forwardmost photo- .graphic element 10 is exposed and wheels 48 are rotated in a counterclockwise direction to advance the forwardmost photographic element into the bite of rolls 42 and 44. Rolls 42 and 44 are then rotated for advancing the photographic element and the print element in superposition therebetween, causing rupture of a container 20 associated with the photographic element and spreading of'the fluid composition 19 contained therein in a thin layer between the two elements to form a sandwich. This sandwich may be advanced directly from the camera through slot 46" and the processing may occur in the presence of environmental light inasmuch as support 16 of each element is opaque to actinic light and the layer of processing composition functions to retain the elements in. superposition with one another. A suitable dye or light-absorbing material may be incorporated in the processing'composition to prevent exposure of the photosensitive material to light entering between the edges of the elements. When processing is complete, the print element containing the finished positive image in a layer of fluid composition 19'is stripped from the photographic element containing the exposed photosensitive layer. The

ruptured container 20 is stripped from this processed photographic element, whichnow comprises an exposed and processed photosensitive layer and a print element. The last-named element is free of fluid composition 19 and may now be introduced into chamber 50 with one end thereof located in the bite of rolls 42 and 44. The print element supporting the image-containing layer of fluid. composition 19 is subjected to a further treatment for protecting the image, and, if the element should include a processed photosensitive layer, then for removing this layer also. The process may then be repeated for the next successive photographic element which is, by virtue of spring 38 and pressure plate 40, located with its photosensitive layer in position for exposure.

The herein disclosed method and apparatus are suited for the production of photographic transparencies as well as forthe production of prints adapted to be viewed by reflected light. Since, in the form of apparatus shown, the first photosensitive element of a stack of elements is exposed in position in the stack, it is important that the element be opaque to actinic light so that successive elements in the stack are not exposed also. When the method of the invention is employed for producing a print to be viewed by reflected light, the support 16 may be opaque as described; but, when it is desirable to produce a transparency, the support must necessarily be transparent. In this case a photographic element includes a support which is transparent and an opaque layer adapted to be removed from the element along with the photosensitive layer. This opaque layer may comprise a separate layer located between photosensitive layer 12 and stripping layer 14 or may be the stripping layer itself.

Since certain changes may be made in the above process without departing from the scope of the invention herein involved, it is intended that all matter contained in the above description or shown in the accompanying drawing shall be interpreted as illustrative and not in a limiting sense.

What is claimed is:

l. A method of producing a sequence of photographic transfer prints requiring the expenditure of only one photographic element for each print produced, and utilizing a pair of said photographic elements during the production of each of said prints, said method including the steps of photoexposing a first photosensitive layer comprising a first photographic element to form an image in said first photosensitive layer, said first element comprising a support layer opaque to light actinic to said photosensitive layer and carrying, on one side, a stripping layer, said photosensitive layer supported on said stripping layer, and a rupturable container of a first fluid processing composition, and, on the other side, a first image-receiving layer; superposing said first photosensitive layer with a second image-receiving layer comprising a second element and moving said first and second elements in superposition relative to and between a pair of juxtaposed pressure-applying members and thereby applying compressive pressure to said container and superposed elements for ejecting said fluid from said container and spreading said fluid in a layer between said elements for permeation into said first photosensitive layer; reacting said fluid with said first photosensitive layer to produce therefrom a visible transfer image carried on said second image-receiving layer; separating said ruptured container and said second element including said second image-receivinglayer, said visible transfer image and said layer of fluid from said first element; photoexposing a second photosensitive layer comprising a third element to form an image in said second photosensitive layer, superposing said first image-receiving layer with said second photosensitive layer and moving said first and third elements in superposition, together with a rupturab le container of a second processing fluid located between said superposed first and third elements, relative to and between a pair of juxtaposed pressure-applying members and thereby applying compressive pressure to said second container and said first and third elements for ejecting said second. fluid from said second container and spreading said second fluid in a layer between said first and third elements for permeation into said second photosensitive layer; reacting said second fluid with said second photosensitive layer to produce therefrom a second visible transfer image carried on said first image-receiving layer; separating said first element including said first photosensitive and image-receiving layers and said second transfer image from said third element including said second photosensitive layer; permeating a third processing fluid including a solvent for said stripping .layer into said stripping layer and thereby dissolving the latter sufliciently to permit said first photosensitive layer to be stripped from the support layer comprising said first elemen-t; and thereafter stripping said first photosensitive layer from the last-mentioned support layer.

2. The photographic method of claim 1 wherein said second photosensitive layer comprises silver halide, said second fluid comprises an alkaline solution including a silver halide developer and a silver halide solvent, said stripping layer comprises a material soluble in an acid solution and insoluble in an alkaline solution, and said third fluid comprises an acid solution.

3. The photographic method of claim 1 wherein said second processing fluid includes a viscous film-forming agent; said second transfer image is formed in said layer of said second fluid; said layer of said second fluid is retained on said first image-receiving layer when said first and third elements are separated; said third fluid includes a reagent for hardening said layer of said second fluid; and said first element including said first imagereceiving layer and said layer of said second fluid is immersed in said third fluid for permeating the latter into said stripping layer and hardening said layer of said second fluid.

4. A method of producing a sequence of photographic transfer prints in a camera, said method requiring the expenditure of only one photographic element for each print produced and utilizing a pair of photographic elements during the production of each of said prints, said pair of elements including at least a first element comprising a photosensitive layer carried on a stripping layer in turn carried on one side of a support layer which is opaque to light actinic to said photosensitive layer, a rupturable container of a processing fluid mounted on the same side of said first element as said photosensitive layer and a print-receiving layer for supporting a diffusion-transfer print carried on the side of said support layer opposite said photosensitive layer; said method including the steps of arranging a plurality of said first elements in stacked relation in a camera with an outermost one of said first elements in position for exposure; photoexposing the photosensitive layer of said one first element to produce an image therein; withdrawing said one first element from exposure position in said stack to permit exposure of the next adjacent first element and,

during withdrawal of said one first element, superposing said photosensitive layer thereof with a print-receiving layer of a second element with said container of said one first element located between the latter and said second element; moving said one first element and said second element in superposition relative to and between a pair of juxtaposed pressure-applying members from said camera and thereby applying compressive pressure to said container and said superposed elements for ejecting said fluid from said container and spreading said fluid in a .-layer between said superposed elements for permeation into said photosensitive layer; reacting said fluid with said photosensitive layer to produce therefrom a first visible diffusion-transfer print supported on said printreceiving layer of said second element; separating said container, said second element and said layer of fluid from said one first element and reintroducing said one first element into said camera to make it available for processing in conjunction with the photosensitive layer of the next adjacent first element; photoexposing the photosensitive layer of the last-mentioned first element to form an image in the photosensitive layer thereof; superposing the last-mentioned photosensitive layer with the print-receiving layer of said one first element and moving -with said last-mentioned photosensitive layer to produce therefrom a second visible diffusion-transfer print supportedon said print-receiving layer of said one first element, and thereafter separating the last-mentioned concontainer, said one first element and the last-mentioned layer of fluid from said last-mentioned first element, thereby making said last-mentioned element available for processing in conjunction with the next succeeding first element to produce another transfer print.

5. The method of claim 3 wherein a third fluid including a solvent for said stripping layer of said one first element is permeated into said stripping layer thereof to dissolve the latter sufficiently to permit said photosensitive layer of said one first element to be stripped from said support layer of said one first element; and thereafter, said photosensitive layer of said one first element is stripped from said support layer of said one first element.

6. The photographic method of claim 4 wherein said second processing fluid includes a viscous film-forming agent, said second transfer print is formed in said layer of said second fluid; said layer of said second fluid is retained on said print-receiving layer of said one first element when the latter is separated from said lastmentioned first element; said third fluid includes a reagent for hardening said layer of said second fluid; and said one first element including said print-receiving layer thereof and said layer of said second fluid is immersed in said third fluid for permeating the latter into said stripping layer of said one first element and hardening said layer of said second fluid.

7. The photographic method of claim 3 wherein said photosensitive layers comprise silver halide, the processing fluid contained in said containers comprising said first elements includes an aqueous alkaline solution of a silver halide developer and a silver halide solvent, said stripping layers of said first elements comprise a material soluble in an acid solution and insoluble in an alkaline solution, and said third fluid comprises an acid solution.

References Cited in the file of this patent UNITED STATES PATENTS 497,884 Krause et a1. May 3, 1893 1,140,877 Cocanari May 25, 1915 2,647,049 Land July 28, 1953 2,662,822 Land Dec. 15, 1953 2,669,516 Land Feb. 16, 1954 2,726,154 Land Dec. 6, 1955 2,740,717 Yutzy et a1. Apr. 3, 1956 

1. A METHOD OF PRODUCING A SEQUENCE OF PHOTOGRAPHIC TRANSFER PRINTS REQUIRING THE EXPENDITURE OF ONLY ONE PHOTOGRAPHIC ELEMENT FOR EACH PRINT PRODUCED, AND UTILIZING A PAIR OF SAID PHOTOGRAPHIC ELEMENTS DURING THE PRODUCTION OF EACH OF SAID PRINTS, SAID METHOD INCLUDING THE STEPS OF PHOTOEXPOSING A FIRST PHOTOSENSITIVE LAYER COMPRISING A FIRST PHOTOGRAPHIC ELEMENT TO FORM AN IMAGE IN SAID FIRST PHOTOSENSITIVE LAYER, SAID FIRST ELEMENT COMPRISING A SUPPORT LAYER OPAQUE TO LIGHT ACTINIC TO SAID PHOTOSENSITIVE LAYER AND CARRYING, ON ONE SIDE, A STRIPPING LAYER, SAID PHOTOSENSITIVE LAYER SUPPORTED ON SAID STRIPPING LAYER, AND A RUPTURABLE CONTAINER OF A FIRST FLUID PROCESSING COMPOSITION, AND, ON THE OTHER SIDE, A FIRST IMAGE-RECEIVING LAYER, SUPERPOSING SAID FIRST PHOTOSENSITIVE LAYER WITH A SECOND IMAGE-RECEIVING LAYER COMPRISING A SECOND ELEMENT AND MOVING SAID FIRST AND SECOND ELEMENTS IN SUPERPOSITION RELATIVE TO AND BETWEEN A PAIR OF JUXTAPOSED PRESSURE-APPLYING MEMBERS AND THEREBY APPLYING COMPRESSIVE PRESSURE TO SAID CONTAINER AND SUPERPOSED ELEMENTS FOR EJECTING SAID FLUID FROM SAID CONTAINER AND SPREADING SAID FLUID IN A LAYER BETWEEN SAID ELEMENTS FOR PERMEATION INTO SAID FIRST PHOTOSENSITIVE LAYER, REACTING SAID FLUID WITH SAID FIRST PHOTOSENSITIVE LAYER TO PRODUCE THEREFROM A VISIBLE TRANSFER IMAGE CARRIED ON SAID SECOND IMAGE-RECEIVING LAYER, SEPARATING SAID RUPTURED CONTAINER AND SAID SECOND ELEMENT INCLUDING SAID SECOND IMAGE-RECEIVING LAYER, SAID VISIBLE TRANSFER IMAGE AND SAID LAYER OF FLUID FROM SAID FIRST ELEMENT, PHOTOEXPOSING A SECOND PHOTOSENSITIVE LAYER COMPRISING A THIRD ELEMENT TO FORM AN IMAGE IN SAID SECOND PHOTOSENSITIVE LAYER 